Long Pitch Helices in Invertebrate Collagens
There are several helicoidal levels in the molecular structure of collagen. The α-chains form left-handed helices wrapped around each other into a super triple helix, which is right-handed. The helical pitches are measured in Angstroms. Other helicoidal orders are observed in the crystalline packing of these triple helices. Our purpose is to consider helicoidal bundles of collagen fibrils, recognizable microscopically (electron or light microscopy), showing therefore much larger helicoidal pitches, such as 0.1 μm or more. Examples are found in numerous invertebrate extracellular matrices. We also intend to analyze geometrical aspects of these systems and to show the close relationship linking these long pitch helices to certain liquid crystalline architectures. The cuticle of certain marine worms will be considered as an example and a general discussion will be introduced about the origin of such helices.
KeywordsCollagen Fibril Tangential Section Cholesteric Liquid Crystal Helical Pitch Pitch Helix
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